Problem: If $a + 7b = 9$ and $x + 3y = 7$, what is $9x + 27y + 5a + 35b$ ?
Explanation: $= 5a + 35b + 9x + 27y$ $= (5) \cdot (a + 7b) + (9) \cdot (x + 3y)$ $= (5) \cdot (9) + (9) \cdot (7)$ $= 45 + 63$ $= 108$